When the Illinois legislature established the first juvenile court in 1899, many reformers had already been focusing on the condition of girls for a long time. Then (as now), girls' misbehaviors were viewed and treated differently from those of boys in the juvenile justice system. Measures taken to shelter girls as the "weaker sex," on one hand, and biases against sexually experienced ("fallen") females, on the other, combined to make their confinements both harsher and longer.

In the juvenile system, a status offense is a misbehavior that is not criminal for adults, such as truancy, running away, unruliness, and involvement in certain sexual acts or associations. By contrast, delinquent behavior includes what for adults are crimes, from larceny (shoplifting) to very serious charges such as burglary, assault, and manslaughter.

In the early 1900s, state authorities used status offense categories to "protect girls." For example, if a juvenile female forced into prostitution was brought to the authorities for safety and shelter, the early Chicago juvenile court might have given her the same treatment as a juvenile convicted of theft by removing her from the jail where she was being detained and committing her to an institution for a lengthy confinement—under conditions that were often brutal. The Industrial School for Girls in Evanston, Ill., was such a "haven"—quite similar to the Geneva Reformatory for Girls where delinquent females were confined.

In the juvenile court's first eight years, almost half the girls ended up being returned to court, compared with only one-fifth of the boys. In 1910, 81 percent of girls were brought to juvenile court either because their "virtue" was "lost" or "in peril." Girls were subjected to pelvic examinations to see whether they had been sexually active or carried a venereal disease. The "morally contaminated" were often isolated from the "innocent," and it was not uncommon for girls to be sexually exploited when being held in the jails and institutions that were supposed to be protecting them.

Ironically, the status offenses and delinquent behaviors of girls brought before juvenile court have proportionately always been of a less-serious nature than those of boys, and they have commonly involved sexually related and gender-specific behaviors such as truancy because of pregnancy or family problems, dating an older male, running away to avoid sexual abuse, and prostitution. In 1995, almost 25 percent of girls' arrests involved status offenses, compared with less than 10 percent for boys. Another 25 percent of girls were charged with shoplifting. When girls in foster care or group-home placements run away, they can be classified as delinquent and incarcerated rather than identified as foster children in the care of special programs or status offenders who cannot be incarcerated.

Additionally, race and economic status have always been factors in the treatment of girls. In 1914 and 1916 in Illinois, the first two "Mary Clubs" were opened for girls who could not return to their parents' homes but wanted to resist commitment to a state institution. They were for white girls only. A Mary Club for girls of color was not opened until 1921. Today, more than half the population in private facilities for girls are white.